The Environmental Protection Agency has been expressing increased concern with the problems resulting from the discharge of fuel vapor from motor vehicles into the atmosphere. At the present time, there are available fuel vapor recovery systems incorporated in the fuel tank vent which typically involve a storage canister which traps vapor which would otherwise be discharged from the tank vent. During operation of the vehicle engine, vapor from the canister is withdrawn from the canister into the engine intake manifold for combustion in the engine.
While such systems minimize the escape of vapor from the tank during normal vehicle operation, they are totally inadequate to cope with the massive surge of fuel vapor displaced from the fuel tank during a refueling operation. To minimize escape of vapor through the vent, these systems invariably employ relatively restricted flow passages which cannot provide adequate venting of the tank head space while the tank is being filled from a service station pump. As a result, even with such systems in place in the vehicle, nearly all of the fuel vapor displaced from the tank during the refueling operation is vented into atmosphere through the fuel tank filler pipe.
It has been proposed to recover fuel vapor displaced from the fuel tank during the refueling operation by a system employing a relatively large vapor receiving canister mounted in the vehicle which is placed in communication with the head space of the fuel tank only during the refueling operation. Such systems permit fuel vapor to be displaced from the tank at a rate of flow which will permit rapid filling of the tank with incoming fuel and will permit the use of a sliding seal between the fill pipe and the standard fuel dispensing nozzle so that the fill pipe is sealed against the discharge of fuel vapor while the tank is being filled. The canister employed by such a system may be connected to the intake manifold in the manner described above so that vapor may be withdrawn for combustion in the engine during operation of the engine.
In present day vehicles, space for mounting the components of a refueling vapor recovery system is limited and the location of available space can vary widely between different makes and models of vehicles. The system, because of the present trend to self service station pumps should be automatically operable and the active parts of the system-that is valves, valve operators, etc. should preferably be contained in a single package conformed to available space on the vehicle so that the package may be mounted at a location which is reasonably accessible for purposes of inspection, repair or replacement.
The present invention is directed to fill neck assemblies which may be coupled to a dual passage tank fill pipe to conduct vapor displaced from the tank during a refilling operation to a remotely located refueling vapor canister.